the reason i sugested 2 perpendicular sets of wires insulated from each other is quite simple, if you imagine a grid made up of the resistive wires that had the x and y axis connected, you would have the same resistance at grid reference C2 as you would at grid reference B3 and so on, just draw a 5 line by 5 line grid and you will see what I mean.
With both x and y insulated, the further you get from your source point, the higher the resistance. Hope that you can follow my thinking on this method
Karl.
I wonder if there is a manufacturer of screens who uses a non-conducting material to physically connect the wires of the screen running perpendicular directions.